In the preferred embodiments of the aforementioned patent and application, an electronic circuit sensing circuit, including a sensing conductor, is located in the appliance housing together with the appliance circuitry, thus eliminating the need for a third conductor to be extended from the plug to the appliance for sensing purposes and avoiding the resulting additional length in sensor conductor that affords an undesirable increase in the reception of radiated energy which may increase the likelihood of false tripping.
In these circuits, an immersion of the appliance causes a short circuit of the power leads through a thyristor, in the sensing circuit, to create a current overload. The plug portion of the circuit includes an interrupter that reacts to the overload by opening both sides of the line.
The initiated overload creates a "crowbar" effect that not only activates the interrupter but acts to limit the current available to the load in substantially immediate fashion, prior to interruption of electrical current. This reduced shock current availability is not readily noted except when such interruption is delayed by special conditions and is of primary importance in its ability to provide protection by limiting available shock current prior to interruption in the event of such delay.
In the aforementioned patent, the overload opens a wire fuse in one side of the line, which is mechanically linked to hold spring loaded contacts closed, to complete the circuit on the other side of the line, and to release them so that they may open when the fuse opens and thus cause both sides of the line to be permanently interrupted.
In the aforementioned patent application the contacts are replaced by a second fuse and the two fuses are mechanically connected so that the opening of one provides a forceful assistance in the opening of the other.
In accordance with the present invention, which relates to the plug section of a preferred embodiment of the IDCI invention disclosed in the above mentioned patent application, the two fuses have a substantially parallel orientation in their mounting, while those in the aforementioned patent application are held at substantially right angles. Also, in the present invention, the mechanical linkage apparatus employed to assure the opening of both fuses when either opens, avoids contact of the assisting element until the moment in which opening assistance is applied. This is to be compared to the elements used to assist opening, as disclosed in the aforementioned patent application, which are in contact prior to the application of opening assistance. While this prior contact can result in more nearly simultaneous opening of the fuses, special heat resisting materials for the fuse contacting areas should be used. Also the assisting spring force is retained directly by fuse tension, rather than by a latching means, as in the present invention, limiting the amount of spring force that can be used to assist in fuse opening and requiring more careful adjustment of fuse tension than the present invention.